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Date: Mon, 7 Dec 2020 14:43:13 +0530 From: Viresh Kumar <viresh.kumar@...aro.org> To: Valentin Schneider <valentin.schneider@....com> Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Vincent Guittot <vincent.guittot@...aro.org>, Amit Daniel Kachhap <amit.kachhap@...il.com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Javi Merino <javi.merino@...nel.org>, Zhang Rui <rui.zhang@...el.com>, Amit Kucheria <amitk@...nel.org>, linux-kernel@...r.kernel.org, Quentin Perret <qperret@...gle.com>, Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org Subject: Re: [PATCH V3 2/2] thermal: cpufreq_cooling: Reuse sched_cpu_util() for SMP platforms Hi Valentin, On 01-12-20, 17:25, Valentin Schneider wrote: > PELT time-scaling can make the util signals behave strangely from an > external PoV. For instance, on a big.LITTLE system, the rq util of a LITTLE > CPU may suddenly drop if it was stuck on a too-low OPP for some time and > eventually reached the "right" OPP (i.e. got idle time). > > Also, as Peter pointed out in [1], task migrations can easily confuse an > external observer that considers util to be "an image of the recent past". I agree with what you wrote and such issues may happen here as they can in case of schedutil as well. The idea behind this patchset was to get the allocator (IPA) and consumer (schedutil) in sync with respect to frequency and power. It is better to allocate the power that schedutil is going to request, then to allocate something based on different metrics. If there is a problem with PELT signal then I will let both the entities suffer with that. -- viresh
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